Direct Evidence for Ca2+Regulation of Hyphal Branch Induction

• Published in: Fungal genetics and biology 1997-10, Vol.22 (2), p.127-139
• Main Authors: Grinberg, Avie, Heath, I.Brent
• Format: Article
• Language: English
• Subjects: branching; Ca2; calcium; cytoplasm; hyphae; inorganic ions; irradiation; regulation; Saprolegnia; Saprolegnia ferax; spatial variation; tip growth; ultraviolet radiation; UV light
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1006/fgbi.1997.1011

Grinberg, A., and Heath, I. B. 1997. Direct evidence for Ca2+regulation of hyphal branch induction.22,127–139. Irradiation of growing hyphae ofSaprolegnia feraxwith microbeams of UV (300–380 and 385–450 nm) light induced an increase in cytoplasmic [Ca2+] followed by precocious formation of one or more branches within about 4 min. The distribution of branches was strongly skewed toward the subapical side of the irradiation site, but otherwise was apparantly random. Apical (10-μm) irradiations were more effective than subapical (50-μm) ones in that they induced branches at comparable frequencies but with lower doses, consistent with higher concentrations of putative target intracellular Ca2+storage structures in this region. Once formed, induced adjacent branches seem to compete for “resources,” with those closer than ≈50 μm inhibiting each other. The results are most consistent with Ca2+-induced accumulation of branch initiating factors being the cause, not the consequence, of branch formation, thus supporting a primary role for Ca2+in regulation of hyphal tip growth.